The present invention generally relates to a computer system for managing volume allocation and to a volume allocation management method, and more particularly, to technology for managing the allocation of physical volumes to main and subsidiary logical volumes in a computer system employing a disaster recovery configuration.
With the digitalization of information, the volume of business data held by computer systems has increased. The loss of business data hampers the continuation of a company's business activities and damages trust in the company, and therefore is a major issue for the company's livelihood. However, the risk of loss of business data always exists, whether through natural disaster, such as an earthquake, or due to terrorist action, or the like. In order to reduce this risk, there are increasing numbers of cases where a disaster recovery configuration is employed in computer systems. Disaster recovery means a configuration whereby a duplicate copy of business data is created in a remote location, on a constant basis during operation, and business can be continued at the remote location using the data copy, in the event of loss of the business data. For example, Japanese Patent Application Publication No. 2009-151389 discloses technology for constructing a disaster recovery configuration using a data duplication function (remote copying function) between frames belonging to a storage system.
Furthermore, in a computer system which duplicates business data on a constant basis during operation, access from a host computer is generally made to the duplication source volume (main logical volume), and therefore the load on this volume is higher than on the duplication destination volume (subsidiary logical volume). For this reason, if the main logical volumes of a plurality of host computers share the same storage apparatus, then the load on that storage apparatus increases. Japanese Patent Application Publication No. 2003-162378 discloses a storage system which generates a plurality of logical volumes from a single physical volume. Japanese Patent Application Publication No. 2003-162378 discloses technology which implements control whereby, in order to avoid increase in the load on a particular physical volume, if a first host computer uses a logical volume that has been generated from a first physical volume as a main logical volume and uses a logical volume that has been generated from a second physical volume as a subsidiary logical volume, then the second host computer uses the logical volume generated from the second physical volume as a main logical volume and uses the logical volume generated from the first physical volume as a subsidiary logical volume.
As an extension of this technology, in order to distribute the load in a disaster recovery configuration as well, in general, a configuration is adopted in which, if a first host computer uses a logical volume stored by a first storage system as a main logical volume and uses a logical volume stored by a second storage system as a subsidiary logical volume, then a second host computer uses a logical volume stored by the second storage system as a main logical volume and uses a logical volume stored by the first storage system as a subsidiary logical volume. In general, this is called an active-active disaster recovery configuration.